Ok, here's what I know about SSSV, Nightmare Creatures, and Body Harvest.
SSSV--I can't for the life of me get that to work on any version of PJ64. I've tried 1.2, 1.3, and of course 1.4. The problem is always the same, the title screen comes up and plays fine, but near the end of the title the FPS display starts dropping lower and lower until the game eventually hangs.???
Nightmare Creatures-- Version 1.2, numerous opcode errors, but the game does run and looks pretty good. I haven't played any more than the opening scene though, so I have no idea what stability is like. Version 1.3, no opcode errors, but most graphics are missing; unplayable. The best bet for this game is the 1.3 core witn the 1.2 video.

lain:
Body Harvest works fine on version 1.3, with a few graphic issues. Haven't got it to start yet in 1.4.
I'm downloading the PAL versions of SSSV and Body Harvest. With any luck those will run on 1.4 (issues similar to Duke Nukem: ZH perhaps? PAL works but US doesn't?). You haven't tried those already have you Smiff?